Linnaeus’ ecology and Darwin’s evolution
“... we can see how Darwin came to recognize that production of new species from old depends not only on natural selection but on the conditions under which selection operates. And this is the important juncture where ecology enters.”
Darwin’s thinking is often summarized as a combination of two theories: natural selection and the theory of descent. Natural selection is described as a process that occurs when more organisms are born than can survive in a certain area. This leads to a struggle for survival. All organisms vary somewhat, and some of these variations provide the individuals with some advantage in the form of better adaptation. The better adapted individuals are those who will be able to reproduce most successfully; they are chosen, so to speak, by nature itself (natural selection). The theory of descent means that offspring inherit the characteristics of their parents and that the various species have evolved from earlier precursors.
According to Darwin, these are the necessary conditions for evolution to occur, but are they also sufficient? No, he answered; his Origin of Species provides a more complicated picture of evolution. Darwin soon realized that new species do not emerge through selection alone; the conditions that selection occurs under must also be factored into the picture. This is where his ecological observations and thoughts become so significant. Selection, the theoretical mechanism behind evolution, does not, after all, take place in a vacuum; it occurs against the background of nature as a whole. It is therefore of interest to study Darwin’s overall view of nature, his ecological thinking, and his philosophy of nature, an aspect that is often neglected by historians.
The sources of Darwin’s protoecological view of nature were numerous. On the one hand, he made early observations of how birds and insects lived in nature, inspired, for example, by the clergyman Gilbert White’s now classic The Natural History of Selborne. White, in turn, was inspired by the Linnaean tradition that had established firm roots in England. He corresponded, for instance, with Linnaeus’ disciple Daniel Solander and Thomas Pennant, the most prominent Welsh zoologist at the time. In the 1830s he encountered these ideas in a more fully developed form by reading the geologist Charles Lyell’s Principia. Lyell was the natural scientist who had best grasped the value of Linnaeus’ protoecological works. “It is the geologist Charles Lyell who shows the clearest grasp of Linnaeus’ ideas on the economy of nature and who makes the fullest use of them in his own work.”
Darwin also encountered Linnaeus’ thinking about the economy of nature when he read Oeconomia Naturae och Politia Naturae in an English translation in the 1840s. It is also during this period that expressions like “husbandry of nature” and “polity of nature” start to become more and more common in his manuscripts and letters, and later in his published books. His thoughts that the various species have “alloted places” or a “proper business” also have counterparts in Linnaeus.
Previously historians have claimed that Darwin got his idea about the “struggle for existence” and the notion of nature’s scarcity, a “population pressure,” from the economist Malthus. But both of these concepts are found in Lyell, in his Principia, and in William Paley’s physicotheological bestseller Natural Theology, books that Darwin had read before he delved into the work of Malthus in 1838. Linnaeus’ Politia Naturae, where the expression “everyone’s war against everyone” occurs, may also have given him the inspiration for this view of nature.